The present invention relates to flea serine protease inhibitor nucleic acid molecules, proteins encoded by such nucleic acid molecules, antibodies raised against such proteins, and inhibitors of such proteins. The present invention also includes therapeutic compositions comprising such nucleic acid molecules, proteins, antibodies, and/or other inhibitors, as well as their use to protect an animal from flea infestation.
Hematophagous ectoparasite infestation of animals is a health and economic concern because hematophagous ectoparasites are known to cause and/or transmit a variety of diseases. Hematophagous ectoparasites directly cause a variety of diseases, including allergies, and also carry a variety of infectious agents including, but not limited to, endoparasites (e.g., nematodes, cestodes, trematodes and protozoa), bacteria and viruses. In particular, the bites of hematophagous ectoparasites are a problem for animals maintained as pets because the infestation becomes a source of annoyance not only for the pet but also for the pet owner who may find his or her home generally contaminated with insects. As such, hematophagous ectoparasites are a problem not only when they are on an animal but also when they are in the general environment of the animal.
Bites from hematophagous ectoparasites are a particular problem because they not only can lead to disease transmission but also can cause a hypersensitive response in animals which is manifested as disease. For example, bites from fleas can cause an allergic disease called flea allergic (or allergy) dermatitis (FAD). A hypersensitive response in animals typically results in localized tissue inflammation and damage, causing substantial discomfort to the animal.
The medical importance of hematophagous ectoparasite infestation has prompted the development of reagents capable of controlling hematophagous ectoparasite infestation. Commonly encountered methods to control hematophagous ectoparasite infestation are generally focused on use of insecticides. While some of these products are efficacious, most offer protection of a very limited duration at best. Furthermore, many of the methods are often not successful in reducing hematophagous ectoparasite populations. In particular, insecticides have been used to prevent hematophagous ectoparasite infestation of animals by adding such insecticides to shampoos, powders, sprays, foggers, collars and liquid bath treatments (i.e., dips). Reduction of hematophagous ectoparasite infestation on the pet has been unsuccessful for one or more of the following reasons: (1) failure of owner compliance (frequent administration is required); (2) behavioral or physiological intolerance of the pet to the pesticide product or means of administration; and (3) the emergence of hematophagous ectoparasite populations resistant to the prescribed dose of pesticide.
Prior investigators have described sequences of a few insect serine protease inhibitors: Bombyx mori nucleic acid and amino acid sequences have been disclosed by Narumi et al., Eur. J. Biochem., 214:181-187, 1993; Takagi et al., J. Biochem., 108:372-378, 1990; and amino acid sequence has been disclosed by Sasaki, Eur. J Biochem, 202:255-261, 1991. Manduca sexta nucleic acid and amino acid sequences have been disclosed by Kanost et al., J. Biol. Chem, 264:965-972, 1989; U.S. Pat. No. 5,436,392, to Thomas et al., issued July 25,-2085, 1990; U.S. Pat. No. 5,196,304, to Kanost et al., issued Mar. 23, 1993; Jiang et al., J. Biol. Chem., 269:55-58, 1994; and Manduca sexta peptide sequences have been disclosed by Fox et al., Peptides, 12:937-944, 1991. Locusta migratoria peptide sequences have been disclosed by Kellenberger et al., J. Biol. Chem, 270:25514-25519, 1995. Rhodnius prolixus peptide sequences have been disclosed by Van De Locht, EMBO, 14:5149-5157, 1995. Lymantria dispar peptide sequences have been disclosed by Valaitis, Insect Biochem Molec Biol, 25:139-149, 1995. Lucilia cuprina nucleic acid and amino acid sequences have been disclosed by Casu et al., Insect Molecular Biology, 3:159-170, 1994. Identification of a serine protease inhibitor of the present invention is unexpected because the most identical amino acid or nucleic acid sequence identified by previous investigators could not be used to identify a flea serine protease inhibitor of the present invention.
In summary, there remains a need to develop a reagent and a method to protect animals from hematophagous ectoparasite infestation.
The present invention relates to a novel product and process for protection of animals from hematophagous ectoparasite infestation. According to the present invention there are provided flea serine protease inhibitor proteins and mimetopes thereof; flea nucleic acid molecules, including those that encode such proteins; antibodies raised against such serine protease inhibitor proteins (i.e., anti-flea serine protease inhibitor antibodies); and other compounds that inhibit flea serine protease inhibitor activity (i.e, inhibitory compounds or inhibitors).
The present invention also includes methods to obtain such proteins, mimetopes, nucleic acid molecules, antibodies and inhibitory compounds. Also included in the present invention are therapeutic compositions comprising such proteins, mimetopes, nucleic acid molecules, antibodies, and/or inhibitory compounds, as well as use of such therapeutic compositions to protect animals from hematophagous ectoparasite infestation.
Identification of a serine protease inhibitor protein of the present invention is unexpected because the most identical amino acid or nucleic acid sequence identified by previous investigators could not be used to identify a flea serine protease inhibitor protein of the present invention. In addition, identification of a flea serine protease inhibitor protein of the present invention is unexpected because a protein fraction from flea prepupal larvae that was obtained by monitoring for carboxylesterase activity surprisingly also contained flea serine protease inhibitor molecular epitopes of the present invention.
One embodiment of the present invention is an isolated flea serine protease nucleic acid molecule that hybridizes under stringent hybridization conditions with a Ctenocephalides felis serine protease inhibitor gene, including, but not limited to, nucleic acid molecules that hybridize under stringent conditions with a nucleic acid molecule having at least one of the following nucleic acid sequences: SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:34, and SEQ ID 35. Particularly preferred flea serine protease inhibitor nucleic acid molecules include nucleic acid sequences SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:34, and SEQ ID 35, and/or nucleic acid sequences encoding proteins having amino acid sequences SEQ ID NO:2, SEQ ID N:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:32, and SEQ ID NO:36, as well as allelic variants of any of the listed nucleic acid sequences or complements of any of the listed nucleic acid sequences.
The present invention also includes an isolated nucleic acid molecule that hybridizes under stringent hybridization conditions with a nucleic acid sequence encoding a protein comprising an amino acid sequence including SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:30, SEQ ID NO:32 and SEQ ID NO:36.
The present invention also relates to recombinant molecules, recombinant viruses and recombinant cells that include flea serine protease inhibitor nucleic acid molecules of the present invention. Also included are methods to produce such nucleic acid molecules, recombinant molecules, recombinant viruses and recombinant cells.
Another embodiment of the present invention includes an isolated flea serine protease inhibitor protein. A preferred flea serine protease inhibitor protein is capable of eliciting an immune response when administered to an animal and/or of having serine protease inhibitor activity. A preferred flea serine protease inhibitor protein is encoded by a nucleic acid molecule that hybridizes under stringent hybridization conditions to a nucleic acid sequence including SEQ ID NO:3, SEQ ID NO:9, SEQ ID NO:15, SEQ ID NO:21, SEQ ID NO:27 and SEQ ID NO:33. Particularly preferred flea serine protease inhibitor proteins include at least one of the following amino acid sequences: SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:30, SEQ ID NO:32, or SEQ ID NO:36.
Yet another embodiment of the present invention is a therapeutic composition that is capable of reducing hematophagous ectoparasite infestation. Such a therapeutic composition includes one or more of the following protective compounds: an isolated flea serine protease inhibitor protein or a mimetope thereof; an isolated nucleic acid molecule that hybridizes under stringent hybridization conditions with a Ctenocephalides felis serine protease inhibitor gene; an isolated antibody that selectively binds to a flea Ctenocephalides felis serine protease inhibitor protein; and an inhibitor of serine protease inhibitor protein activity identified by its ability to inhibit flea serine protease inhibitor activity, such as, but not limited to, a substrate analog of a flea serine protease inhibitor protein. A preferred therapeutic composition of the present invention also includes an excipient, an adjuvant and/or a carrier. Also included in the present invention is a method to reduce flea infestation. The method includes the step of administering to the animal a therapeutic composition of the present invention.
The present invention also includes an inhibitor of serine protease inhibitor protein activity identified by its ability to inhibit the activity of a flea serine protease inhibitor protein. An example of such an inhibitor is a substrate analog of a flea serine protease inhibitor protein. Also included in the present invention are mimetopes of flea serine protease inhibitor proteins of the present invention identified by their ability to inhibit flea serine protease activity.
Yet another embodiment of the present invention is a method to identify a compound capable of inhibiting flea serine protease inhibitor activity. The method includes the steps of: (a) contacting an isolated flea serine protease inhibitor protein with a putative inhibitory compound under conditions in which, in the absence of the compound, the protein has serine protease inhibitor activity; and (b) determining if the putative inhibitory compound inhibits the activity. Also included in the present invention is a test kit to identify a compound capable of inhibiting flea serine protease inhibitor activity. Such a kit includes an isolated flea serine protease inhibitor protein having serine protease inhibitor activity and a means for determining the extent of inhibition of the activity in the presence of a putative inhibitory compound.
Yet another embodiment of the present invention is a method to produce a flea serine protease inhibitor protein, the method comprising culturing a cell transformed with a nucleic acid molecule that hybridizes under stringent hybridization conditions with a Ctenocephalides felis serine protease inhibitor gene.
The present invention provides for isolated flea serine protease inhibitor (SPI) proteins, isolated flea serine protease inhibitor nucleic acid molecules, antibodies directed against flea serine protease inhibitor proteins and other inhibitors of flea serine protease inhibitor activity. As used herein, the terms isolated flea serine protease inhibitor proteins and isolated flea serine protease inhibitor nucleic acid molecules refers to serine protease inhibitor proteins and serine protease inhibitor nucleic acid molecules derived from fleas and, as such, can be obtained from their natural source or can be produced using, for example, recombinant nucleic acid technology or chemical synthesis. A SPI protein can have the ability to inhibit the proteolytic activity of a serine protease protein. A protein denoted as a SPI protein can also possess cysteine protease activity, in addition to serine protease activity. Also included in the present invention is the use of these proteins, nucleic acid molecules, antibodies and other inhibitors as therapeutic compositions to protect animals from hematophagous ectoparasite infestation as well as in other applications, such as those disclosed below.
Flea serine protease inhibitor proteins and nucleic acid molecules of the present invention have utility because they represent novel targets for anti-hematophagous ectoparasite vaccines and drugs. The products and processes of the present invention are advantageous because they enable the inhibition of hematophagous ectoparasite serine protease activity necessary for hematophagous ectoparasite survival or the inhibition of serine protease inhibitors, thereby deregulating serine protease activity, leading to uncontrolled proteolysis of an hematophagous ectoparasite.
One embodiment of the present invention is an isolated protein comprising a flea SPI protein. It is to be noted that the term xe2x80x9caxe2x80x9d or xe2x80x9canxe2x80x9d entity refers to one or more of that entity; for example, a protein refers to one or more proteins or at least one protein. As such, the terms xe2x80x9caxe2x80x9d (or xe2x80x9canxe2x80x9d), xe2x80x9cone or morexe2x80x9d and xe2x80x9cat least onexe2x80x9d can be used interchangeably herein. It is also to be noted that the terms xe2x80x9ccomprisingxe2x80x9d, xe2x80x9cincludingxe2x80x9d, and xe2x80x9chavingxe2x80x9d can be used interchangeably. Furthermore, a compound xe2x80x9cselected from the group consisting ofxe2x80x9d refers to one or more of the compounds in the list that follows, including mixtures (i.e., combinations) of two or more of the compounds. According to the present invention, an isolated, or biologically pure, protein, is a protein that has been removed from its natural milieu. As such, xe2x80x9cisolatedxe2x80x9d and xe2x80x9cbiologically purexe2x80x9d do not necessarily reflect the extent to which the protein has been purified. An isolated protein of the present invention can be obtained from its natural source, can be produced using recombinant DNA technology or can be produced by chemical synthesis.
As used herein, an isolated flea SPI protein can be a full-length protein or any homolog of such a protein. An isolated protein of the present invention, including a homolog, can be identified in a straight-forward manner by the protein""s ability to elicit an immune response against flea SPI proteins and/or ability to inhibit, or reduce, serine protease activity. Examples of serine protease inhibitor homologs include SPI proteins in which amino acids have been deleted (e.g., a truncated version of the protein, such as a peptide), inserted, inverted, substituted and/or derivatized (e.g., by glycosylation, phosphorylation, acetylation, myristoylation, prenylation, palmitoylation, amidation and/or addition of glycerophosphatidyl inositol) such that the homolog includes at least one epitope capable of eliciting an immune response against a flea protein or has at least some serine protease inhibitor activity. For example, when the homolog is administered to an animal as an immunogen, using techniques known to those skilled in the art, the animal will produce an immune response against at least one epitope of a natural flea SPI protein. The ability of a protein to effect an immune response, can be measured using techniques known to those skilled in the art. Techniques to measure serine protease inhibitor activity are also known to those skilled in the art; see, for example, Jiang et al., 1995, Insect Biochem. Molec. Biol. 25, 1093-1100.
Flea SPI protein homologs can be the result of natural allelic variation or natural mutation. SPI protein homologs of the present invention can also be produced using techniques known in the art including, but not limited to, direct modifications to the protein or modifications to the gene encoding the protein using, for example, classic or recombinant nucleic acid techniques to effect random or targeted mutagenesis.
Isolated SPI proteins of the present invention have the further characteristic of being encoded by nucleic acid molecules that hybridize under stringent hybridization conditions to a gene encoding a Ctenocephalides felis SPI protein (i.e., a C. felis SPI gene). As used herein, stringent hybridization conditions refer to standard hybridization conditions under which nucleic acid molecules, including oligonucleotides, are used to identify similar nucleic acid molecules. Such standard conditions are disclosed, for example, in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Labs Press, 1989; Sambrook et al., ibid., is incorporated by reference herein in its entirety. Stringent hybridization conditions typically permit isolation of nucleic acid molecules having at least about 70% nucleic acid sequence identity with the nucleic acid molecule being used to probe in the hybridization reaction. Formulae to calculate the appropriate hybridization and wash conditions to achieve hybridization permitting 30% or less mismatch of nucleotides are disclosed, for example, in Meinkoth et al., 1984, Anal. Biochem. 138, 267-284; Meinkoth et al., ibid., is incorporated by reference herein in its entirety.
As used herein, a C. felis SPI gene includes all nucleic acid sequences related to a natural C. felis SPI gene such as regulatory regions that control production of the C. felis SPI protein encoded by that gene (such as, but not limited to, transcription, translation or post-translation control regions) as well as the coding region itself. In one embodiment, a C. felis SPI gene of the present invention includes the nucleic acid sequence SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:31 and/or SEQ ID NO:33. Nucleic acid sequence SEQ ID NO:1 represents the deduced sequence of the coding strand of a complementary DNA (cDNA) nucleic acid molecule denoted herein as nfSPI11584, the production of which is disclosed in the Examples. The complement of SEQ ID NO:1 (represented herein by SEQ ID NO:3) refers to the nucleic acid sequence of the strand complementary to the strand having SEQ ID NO:1, which can easily be determined by those skilled in the art. Likewise, a nucleic acid sequence complement of any nucleic acid sequence of the present invention refers to the nucleic acid sequence of the nucleic acid strand that is complementary to (i.e., can form a complete double helix with) the strand for which the sequence is cited.
Nucleic acid sequence SEQ ID NO:7 represents the deduced sequence of the coding strand of a cDNA nucleic acid molecule denoted herein as nfSPI21358, the production of which is disclosed in the Examples. The complement of SEQ ID NO:7 is represented herein by SEQ ID NO:9.
Nucleic acid sequence SEQ ID NO:13 represents the deduced sequence of the coding strand of a cDNA nucleic acid molecule denoted herein as nfSPI31838, the production of which is disclosed in the Examples. The complement of SEQ ID NO:13 is represented herein by SEQ ID NO:15.
Nucleic acid sequence SEQ ID NO:19 represents the deduced sequence of the coding strand of a cDNA nucleic acid molecule denoted herein as nfSPI41414, the production of which is disclosed in the Examples. The complement of SEQ ID NO:19 is represented herein by SEQ ID NO:21.
Nucleic acid sequence SEQ ID NO:25 represents the deduced sequence of the coding strand of a cDNA nucleic acid molecule denoted herein as nfSPI51492, the production of which is disclosed in the Examples. The complement of SEQ ID NO:25 is represented herein by SEQ ID NO:27.
Nucleic acid sequence SEQ ID NO:31 represents the deduced sequence of the coding strand of a cDNA nucleic acid molecule denoted herein as nfSPI61454, the production of which is disclosed in the Examples. The complement of SEQ ID NO:31 is represented herein by SEQ ID NO:33.
It should be noted that since nucleic acid sequencing technology is not entirely error-free, SEQ ID NO:1, SEQ ID NO:7, SEQ ID NO:13, SEQ ID NO:19, SEQ ID NO:25 and SEQ ID NO:31, and complements thereof (as well as other nucleic acid and protein sequences presented herein), at best, represent apparent nucleic acid sequences of certain nucleic acid molecules encoding C. felis SPI proteins of the present invention.
In another embodiment, a C. felis SPI gene can be an allelic variant that includes a similar but not identical sequence to SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:34, and/or SEQ ID 35. An allelic variant of a C. felis SPI gene is a gene that occurs at essentially the same locus (or loci) in the genome as the gene including SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:34 and SEQ ID NO:35, but which, due to natural variations caused by, for example, mutation or recombination, has a similar but not identical sequence. Allelic variants typically encode proteins having similar activity to that of the protein encoded by the gene to which they are being compared. Allelic variants can also comprise alterations in the 5xe2x80x2 or 3xe2x80x2 untranslated regions of the gene (e.g., in regulatory control regions). Allelic variants are well known to those skilled in the art and would be expected to be found within a given flea since the genome is diploid and/or among a group of two or more fleas.
The minimal size of a SPI protein homolog of the present invention is a size sufficient to be encoded by a nucleic acid molecule capable of forming a stable hybrid (i.e., hybridize under stringent hybridization conditions) with the complementary sequence of a nucleic acid molecule encoding the corresponding natural protein. As such, the size of the nucleic acid molecule encoding such a protein homolog is dependent on nucleic acid composition and percent homology between the nucleic acid molecule and complementary sequence. It should also be noted that the extent of homology required to form a stable hybrid can vary depending on whether the homologous sequences are interspersed throughout the nucleic acid molecules or are clustered (i.e., localized) in distinct regions on the nucleic acid molecules. The minimal size of such nucleic acid molecules is typically at least about 12 to about 15 nucleotides in length if the nucleic acid molecules are GC-rich and at least about 15 to about 17 bases in length if they are AT-rich. As such, the minimal size of a nucleic acid molecule used to encode a SPI protein homolog of the present invention is from about 12 to about 18 nucleotides in length. Thus, the minimal size of a SPI protein homolog of the present invention is from about 4 to about 6 amino acids in length. There is no limit, other than a practical limit, on the maximal size of such a nucleic acid molecule in that the nucleic acid molecule can include a portion of a gene, an entire gene, multiple genes, or portions thereof. The preferred size of a protein encoded by a nucleic acid molecule of the present invention depends on whether a full-length, fusion, multivalent, or functional portion of such a protein is desired.
Suitable fleas from which to isolate SPI proteins of the present invention (including isolation of the natural protein or production of the protein by recombinant or synthetic techniques) include Ctenocephalides, Ceratophyllus, Diamanus, Echidnophaga, Nosopsyllus, Pulex, Tunga, Oropsylla, Orchopeus and Xenopsylla. More preferred fleas from which to isolate SPI proteins include Ctenocephalides felis, Ctenocephalides canis, Ceratophyllus pulicidae, Pulex irritans, Oropsylla (Thrassis) bacchi, Oropsylla (Diamanus) montana, Orchopeus howardi, Xenopsylla cheopis and Pulex simulans, with C. felis being even more preferred.
Suitable flea tissues from which to isolate a SPI protein of the present invention includes tissues from unfed fleas or tissue from fleas that recently consumed a blood meal (i.e., blood-fed fleas). Such flea tissues are referred to herein as, respectively, unfed flea tissues and fed flea tissues. Preferred flea tissues from which to obtain a SPI protein of the present invention includes unfed or fed pre-pupal larval, 1st instar larval, 2nd instar larval, 3rd instar larval, and/or adult flea tissues. More preferred flea tissue includes prepupal larval tissue. A SPI of the present invention is also preferably obtained from hemolymph.
A preferred flea SPI protein of the present invention is a compound that when administered to an animal in an effective manner, is capable of protecting that animal from a hematophagous ectoparasite infestation. In accordance with the present invention, the ability of a SPI protein of the present invention to protect an animal from a hematophagous ectoparasite infestation refers to the ability of that protein to, for example, treat, ameliorate and/or prevent infestation caused by a hematophagous ectoparasite. In particular, the phrase xe2x80x9cto protect an animal from hematophagous ectoparasite infestationxe2x80x9d refers to reducing the potential for hematophagous ectoparasite population expansion on and around the animal (i.e., reducing the hematophagous ectoparasite burden). Preferably, the hematophagous ectoparasite population size is decreased, optimally to an extent that the animal is no longer bothered by hematophagous ectoparasites. A host animal, as used herein, is an animal from which hematophagous ectoparasites can feed by attaching to and feeding through the skin of the animal. Hematophagous ectoparasites, and other ectoparasites, can live on a host animal for an extended period of time or can attach temporarily to an animal in order to feed. At any given time, a certain percentage of a hematophagous ectoparasite population can be on a host animal whereas the remainder can be in the environment of the animal. Such an environment can include not only adult hematophagous ectoparasites, but also hematophagous ectoparasite eggs and/or hematophagous ectoparasite larvae. The environment can be of any size such that hematophagous ectoparasite in the environment are able to jump onto and off of a host animal. For example, the environment of an animal can include plants, such as crops, from which hematophagous ectoparasites infest an animal. As such, it is desirable not only to reduce the hematophagous ectoparasite burden on an animal per se, but also to reduce the hematophagous ectoparasite burden in the environment of the animal. In one embodiment, a SPI protein of the present invention can elicit an immune response (including a humoral and/or cellular immune response) against a hematophagous ectoparasite.
Suitable hematophagous ectoparasites to target include any hematophagous ectoparasite that is essentially incapable of infesting an animal administered a SPI protein of the present invention. As such, a hematophagous ectoparasite to target includes any hematophagous ectoparasite that produces a protein having one or more epitopes that can be targeted by a humoral and/or cellular immune response against a SPI protein of the present invention, that can be targeted by a compound that otherwise inhibits SPI activity, and/or that can be targeted by a SPI protein (e.g., a peptide) or mimetope of a SPI protein of the present invention in such a manner as to inhibit serine protease activity, thereby resulting in the decreased ability of the hematophagous ectoparasite to infest an animal. Preferred hematophagous ectoparasite to target include insects and acarines. A SPI protein of the present invention preferably protects an animal from infestation by hematophagous ectoparasites including, but are not limited to, agricultural pests, stored product pests, forest pests, structural pests or animal health pests. Suitable agricultural pests of the present invention include, but are not limited to, Colorado potato beetles, corn earworms, fleahoppers, weevils, pink boll worms, cotton aphids, beet armyworms, lygus bugs, hessian flies, sod webworms, whites grubs, diamond back moths, white flies, planthoppers, leafhoppers, mealy bugs, mormon crickets and mole crickets. Suitable stored product pests of the present invention include, but are not limited to, dermestids, anobeids, saw toothed grain beetles, indian mealmoths, flour beetles, long-horn wood boring beetles and metallic wood boring beetles. Suitable forest pests of the present invention include, but are not limited to, southern pine bark beetles, gypsy moths, elm beetles, ambrosia bettles, bag worms, tent worms and tussock moths. Suitable structural pests of the present invention include, but are not limited to, bess beetles, termites, fire ants, carpenter ants, wasps, hornets, cockroaches, silverfish, Musca domestica and Musca autumnalis. Suitable animal health pests of the present invention include, but are not limited to, fleas, ticks, mosquitoes, black flies, lice, true bugs, sand flies, Psychodidae, tsetse flies, sheep blow flies, cattle grub, mites, horn flies, heel flies, deer flies, Culicoides and warble flies. A SPI protein of the present invention more preferably protects an animal from infestation by hematophagous ectoparasites including fleas, midges, mosquitos, sand flies, black flies, horse flies, snipe flies, louse flies, horn flies, deer flies, tsetse flies, buffalo flies, blow flies, stable flies, myiasis-causing flies, biting gnats, lice, mites, bee, wasps, ants, true bugs and ticks, even more preferably fleas and ticks, and even more preferably fleas. Preferred fleas from which to protect an animal from flea infestation include those disclosed herein for the isolation of a SPI of the present invention.
The present invention also includes mimetopes of SPI proteins of the present invention. As used herein, a mimetope of a SPI protein of the present invention refers to any compound that is able to mimic the activity of such a SPI protein (e.g., ability to elicit an immune response against a SPI protein of the present invention and/or ability to inhibit serine protease activity), often because the mimetope has a structure that mimics the SPI protein. It is to be noted, however, that the mimetope need not have a structure similar to an SPI protein as long as the mimetope functionally mimics the protein. Mimetopes can be, but are not limited to: peptides that have been modified to decrease their susceptibility to degradation; anti-idiotypic and/or catalytic antibodies, or fragments thereof; non-proteinaceous immunogenic portions of an isolated protein (e.g., carbohydrate structures); synthetic or natural organic or inorganic molecules, including nucleic acids; and/or any other peptidomimetic compounds. Mimetopes of the present invention can be designed using computer-generated structures of SPI proteins of the present invention. Mimetopes can also be obtained by generating random samples of molecules, such as oligonucleotides, peptides or other organic molecules, and screening such samples by affinity chromatography techniques using the corresponding binding partner, (e.g., a flea serine protease or anti-flea serine protease inhibitor antibody). A preferred mimetope is a peptidomimetic compound that is structurally and/or functionally similar to a SPI protein of the present invention, particularly to the active site of the SPI protein.
One embodiment of a flea SPI protein of the present invention is a fusion protein that includes a flea SPI protein-containing domain attached to one or more fusion segments. Suitable fusion segments for use with the present invention include, but are not limited to, segments that can: enhance a protein""s stability; act as an immunopotentiator to enhance an immune response against a SPI protein; and/or assist purification of a SPI protein (e.g., by affinity chromatography). A suitable fusion segment can be a domain of any size that has the desired function (e.g., imparts increased stability, imparts increased immunogenicity to a protein, and/or simplifies purification of a protein). Fusion segments can be joined to amino and/or carboxyl termini of the SPI-containing domain of the protein and can be susceptible to cleavage in order to enable straight-forward recovery of a SPI protein. Fusion proteins are preferably produced by culturing a recombinant cell transformed with a fusion nucleic acid molecule that encodes a protein including the fusion segment attached to either the carboxyl and/or amino terminal end of a SPI-containing domain. Preferred fusion segments include a metal binding domain (e.g., a poly-histidine segment); an immunoglobulin binding domain (e.g., Protein A; Protein G; T cell; B cell; Fc receptor or complement protein antibody-binding domains); a sugar binding domain (e.g., a maltose binding domain); and/or a xe2x80x9ctagxe2x80x9d domain (e.g., at least a portion of xcex2-galactosidase, a strep tag peptide, other domains that can be purified using compounds that bind to the domain, such as monoclonal antibodies). More preferred fusion segments include metal binding domains, such as a poly-histidine segment; a maltose binding domain; a strep tag peptide, such as that available from Biometra in Tampa, Fla.; and an S10 peptide. Examples of particularly preferred fusion proteins of the present invention include PHis-PfSPI2376, PHis-PfSPI3390, PHis-PfSPI4376, and PHis-PfSPI6376, production of which are disclosed herein.
In another embodiment, a flea SPI protein of the present invention also includes at least one additional protein segment that is capable of protecting an animal from hematophagous ectoparasite infestations. Such a multivalent protective protein can be produced by culturing a cell transformed with a nucleic acid molecule comprising two or more nucleic acid domains joined together in such a manner that the resulting nucleic acid molecule is expressed as a multivalent protective compound containing at least two protective compounds, or portions thereof, capable of protecting an animal from hematophagous ectoparasite infestation by, for example, targeting two different flea proteins.
Examples of multivalent protective compounds include, but are not limited to, a SPI protein of the present invention attached to one or more compounds protective against one or more flea compounds. Preferred second compounds are proteinaceous compounds that effect active immunization (e.g., antigen vaccines), passive immunization (e.g., antibodies), or that otherwise inhibit a hematophagous ectoparasite activity that when inhibited can reduce hematophagous ectoparasite burden on and around an animal. Examples of second compounds include a compound that inhibits binding between a flea protein and its ligand (e.g., a compound that inhibits flea ATPase activity or a compound that inhibits binding of a peptide or steroid hormone to its receptor), a compound that inhibits hormone (including peptide or steroid hormone) synthesis, a compound that inhibits vitellogenesis (including production of vitellin and/or transport and maturation thereof into a major egg yolk protein), a compound that inhibits fat body function, a compound that inhibits muscle action, a compound that inhibits the nervous system, a compound that inhibits the immune system and/or a compound that inhibits flea feeding. Particular examples of second compounds include, but are not limited to, serine proteases, cysteine proteases, aminopeptidases, calreticulins and esterases, as well as antibodies and inhibitors of such proteins. In one embodiment, a flea SPI protein of the present invention is attached to one or more additional compounds protective against hematophagous ectoparasite infestation. In another embodiment, one or more protective compounds, such as those listed above, can be included in a multivalent vaccine comprising a flea SPI protein of the present invention and one or more other protective molecules as separate compounds.
A preferred flea SPI protein of the present invention is encoded by a nucleic acid molecule that hybridizes under stringent hybridization conditions with at least one of the following nucleic acid molecules: nfSPI11584, nfSPI11191, nfSPI1376, nfSPI21358, nfSPI21197, nfSPI2376, nfSPI31838, nfSPI31260, nfSPI3391, nfSPI41414, nfSPI41179, nfSPI4376, nfSPI51492, nfSPI51194, nfSPI5376, nfSPI61454, nfSPI61191 and nfSPI6376. A further preferred isolate protein is encoded by a nucleic acid molecule that hybridizes under stringent hybridization conditions with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:27 SEQ ID NO:29, SEQ ID NO:33 and SEQ ID NO:35.
Translation of SEQ ID NO:1 suggests that nucleic acid molecule nfSPI11584 encodes a full-length flea protein of about 397 amino acids, referred to herein as PfSPI1397, represented by SEQ ID NO:2, assuming an open reading frame having an initiation (start) codon spanning from about nucleotide 136 through about nucleotide 138 of SEQ ID NO:1 and a termination (stop) codon spanning from about nucleotide 1327 through about nucleotide 1329 of SEQ ID NO:1. The coding region encoding PfSPI1397 is represented by nucleic acid molecule nfSPI11191, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:4 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:5. The deduced amino acid sequence SEQ ID NO:2 suggests a protein having a molecular weight of about 44.4 kilodaltons (kD) and an estimated pI of about 4.97. Analysis of SEQ ID NO:2 suggests the presence of a signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 21. The proposed mature protein, denoted herein as PfSPI1376, contains about 376 amino acids which is represented herein as SEQ ID NO:6. The amino acid sequence of flea PfSPI1376 (i.e. SEQ ID NO:6) predicts that PfSPI1376 has an estimated molecular weight of about 42.1 kD, an estimated pI of about 4.90, and a predicted asparagine-linked glycosylation site extending from about amino acid 252 to about amino acid 254.
Comparison of amino acid sequence SEQ ID NO:2 (i.e., the amino acid sequence of PfSPI1397) with amino acid sequences reported in GenBank indicates that SEQ ID NO:2 showed the most homology, i.e., about 36% identity, with GenBank accession number 1378131, a serpin protein from Manduca sexta. 
Translation of SEQ ID NO:7 suggests that nucleic acid molecule nfSPI21358 encodes a non-full-length flea SPI protein of about 399 amino acids, referred to herein as PfSPI2399, represented by SEQ ID NO:8, assuming an open reading frame having a first in-frame codon spanning from about nucleotide 2 through about nucleotide 4 of SEQ ID NO:7 and a termination codon spanning from about nucleotide 1199 through about nucleotide 1201 of SEQ ID NO:7. The coding region encoding PfSPI2399 is represented by nucleic acid molecule nfSPI21197, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:10 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:11. Analysis of SEQ ID NO:8 suggests the presence of a partial signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 23. The proposed mature protein, denoted herein as PfSPI2376, contains about 376 amino acids which is represented herein as SEQ ID NO:12. The amino acid sequence of flea PfSPI1376 (i.e. SEQ ID NO:12) predicts that PfSPI2376 has an estimated molecular weight of about 42.1 kD, an estimated pI of about 4.87, and a predicted asparagine-linked glycosylation site extending from about amino acid 252 to about amino acid 254.
Comparison of amino acid sequence SEQ ID NO:8 (i.e., the amino acid sequence of PfSPI2399) with amino acid sequences reported in GenBank indicates that SEQ ID NO:8, showed the most homology, i.e., about 36% identity, with GenBank accession number 1345616, a serpin protein from Homo sapiens. 
Translation of SEQ ID NO:13 suggests that nucleic acid molecule nfSPI31838 encodes a full-length flea SPI protein of about 420 amino acids, referred to herein as PfSPI3420, represented by SEQ ID NO:14, assuming an open reading frame having an initiation codon spanning from about nucleotide 306 through about nucleotide 308 of SEQ ID NO:13 and a termination codon spanning from about nucleotide 1566 through about nucleotide 1568 of SEQ ID NO:13. The coding region encoding PfSPI3420 is represented by nucleic acid molecule nfSPI31260, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:16 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:17. The deduced amino acid sequence SEQ ID NO:14 suggests a protein having a molecular weight of about 47.1 kilodaltons (kD) and an estimated pI of about 4.72. Analysis of SEQ ID NO:14 suggests the presence of a signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 30. The proposed mature protein, denoted herein as PfSPI3390, contains about 390 amino acids which is represented herein as SEQ ID NO:18. The amino acid sequence of flea PfSPI3390 (i.e. SEQ ID NO:18) predicts that PfSPI3390 has an estimated molecular weight of about 43.7 kD, an estimated pI of about 4.63, and two predicted asparagine-linked glycosylation sites extending from about amino acid 252 to about amino acid 254 and from about amino acid 369 to about amino acid 371.
Comparison of amino acid sequence SEQ ID NO:14 (i.e., the amino acid sequence of PfSPI3420) with amino acid sequences reported in GenBank indicates that SEQ ID NO:14, showed the most homology, i.e., about 35% identity, with GenBank accession number 1345616, a serpin protein from Homo sapiens. 
Translation of SEQ ID NO:19 suggests that nucleic acid molecule nfSPI41414 encodes a non-full-length flea SPI protein of about 393 amino acids, referred to herein as PfSPI4393, represented by SEQ ID NO:20, assuming an open reading frame having a first in-frame codon spanning from about nucleotide 2 through about nucleotide 4 of SEQ ID NO:19 and a termination codon spanning from about nucleotide 1181 through about nucleotide 1183 of SEQ ID NO:19. The coding region encoding PfSPI4393, is represented by nucleic acid molecule nfSPI41179, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:22 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:23. Analysis of SEQ ID NO:20 suggests the presence of a partial signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 17. The proposed mature protein, denoted herein as PfSPI4376, contains about 376 amino acids which is represented herein as SEQ ID NO:24. The amino acid sequence of flea PfSPI4376 (i.e. SEQ ID NO:24) predicts that PfSPI4376 has an estimated molecular weight of about 42.2 kD, an estimated pI of about 5.31, and a predicted asparagine-linked glycosylation site extending from about amino acid 252 to about amino acid 254.
Comparison of amino acid sequence SEQ ID NO:20 (i.e., the amino acid sequence of PfSPI4393) with amino acid sequences reported in GenBank indicates that SEQ ID NO:20, showed the most homology, i.e., about 38% identity, with GenBank accession number 1345616, a serpin protein from Homo sapiens. 
Translation of SEQ ID NO:25 suggests that nucleic acid molecule nfSPI51492 encodes a non-full-length flea SPI protein of about 398 amino acids, referred to herein as PfSPI5398, represented by SEQ ID NO:26, assuming an open reading frame having a first in-frame codon spanning from about nucleotide 3 through about nucleotide 5 of SEQ ID NO:25 and a termination codon spanning from about nucleotide 1197 through about nucleotide 1199 of SEQ ID NO:25. The coding region encoding PfSPI5398, is represented by nucleic acid molecule nfSPI51194, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:28 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:29. Analysis of SEQ ID NO:26 suggests the presence of a partial signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 22. The proposed mature protein, denoted herein as PfSPI5376, contains about 376 amino acids which is represented herein as SEQ ID NO:30. The amino acid sequence of flea PfSPI5376 (i.e. SEQ ID NO:30) predicts that PfSPI5376 has an estimated molecular weight of about 42.3 kD, an estimated pI of about 5.31 and a predicted asparagine-linked glycosylation site extending from about amino acid 252 to about amino acid 254.
Comparison of amino acid sequence SEQ ID NO:26 (i.e., the amino acid sequence of PfSPI5398) with amino acid sequences reported in GenBank indicates that SEQ ID NO:26 showed the most homology, i.e., about 38% identity with GenBank accession number 1345616, a serpin protein from Homo sapiens. 
Translation of SEQ ID NO:31 suggests that nucleic acid molecule nfSPI61454 encodes a full-length flea SPI protein of about 397 amino acids, referred to herein as PfSPI6397, represented by SEQ ID NO:32, assuming an open reading frame having an initiation codon spanning from about nucleotide 20 through about nucleotide 22 of SEQ ID NO:31 and a termination codon spanning from about nucleotide 1211 through about nucleotide 1213 of SEQ ID NO:31. The coding region encoding PfSPI6397 is represented by nucleic acid molecule nfSPI61191, having a coding strand with the nucleic acid sequence represented by SEQ ID NO:34 and a complementary strand with the nucleic acid sequence represented by SEQ ID NO:35. The deduced amino acid sequence SEQ ID NO:32 suggests a protein having a molecular weight of about 44.4 kilodaltons (kD) and an estimated pI of about 4.90. Analysis of SEQ ID NO:32 suggests the presence of a signal peptide encoded by a stretch of amino acids spanning from about amino acid 1 through about amino acid 21. The proposed mature protein, denoted herein as PfSPI6376, contains about 376 amino acids which is represented herein as SEQ ID NO:36. The amino acid sequence of flea PfSPI6376 (i.e. SEQ ID NO:36) predicts that PfSPI6376 has an estimated molecular weight of about 42.1 kD, an estimated pI of about 4.84, and a predicted asparagine-linked glycosylation site extending from about amino acid 252 to about amino acid 254.
Comparison of amino acid sequence SEQ ID NO:32 (i.e., the amino acid sequence of PfSPI6397) with amino acid sequences reported in GenBank indicates that SEQ ID NO:32 showed the most homology, i.e., about 36% identity with GenBank accession number 1378131, a serpin protein from Manduca sexta. 
More preferred flea SPI proteins of the present invention include proteins comprising amino acid sequences that are at least about 40%, preferably at least about 50%, more preferably at least about 60%, more preferably at least about 70%, more preferably at least about 80%, and even more preferably at least about 90%, identical to amino acid sequence SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:30, SEQ ID NO:32 and/or SEQ ID NO:36.
More preferred flea SPI proteins of the present invention include proteins encoded by a nucleic acid molecule comprising at least a portion of nfSPI11584, nfSPI21358, nfSPI31838, nfSPI41414, nfSPI51492, and nfSPI61454, or of allelic variants of such nucleic acid molecules. More preferred is a SPI protein encoded by nfSPI11584, nfSPI11191, nfSPI1376, nfSPI21358, nfSPI21197, nfSPI2376, nfSPI31838, nfSPI31260, nfSPI3391, nfSPI41414, nfSPI41179, nfSPI4376, nfSPI51492, nfSPI51194, nfSPI5376, nfSPI61454, nfSPI61191, or nfSPI6376, or by an allelic variant of such nucleic acid molecules. Particularly preferred flea SPI proteins are PfSPI1397, PfSPI1376, PfSPI2399, PfSPI2376, PfSPI3420, PfSPI3391, PfSPI4393, PfSPI4376, PfSPI5398, PfSPI5376, PfSPI6397 and PfSPI6376.
In one embodiment, a preferred SPI protein of the present invention is encoded by at least a portion of SEQ ID NO:1, SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:10, SEQ ID NO:13, SEQ ID NO:16, SEQ ID NO:19, SEQ ID NO:22, SEQ ID NO:25, SEQ ID NO:28, SEQ ID NO:31 and/or SEQ ID NO:34, and, as such, has an amino acid sequence that includes at least a portion of SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO30, SEQ ID NO:32 and SEQ ID NO:36, respectively.
Also preferred is a protein encoded by an allelic variant of a nucleic acid molecule comprising at least a portion of SEQ ID NO:1, SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:10, SEQ ID NO:13, SEQ ID NO:16, SEQ ID NO:19, SEQ ID NO:22, SEQ ID NO:25, SEQ ID NO:28, SEQ ID NO:31 and/or SEQ ID NO:34. Particularly preferred SPI proteins of the present invention include SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO30, SEQ ID NO:32 and SEQ ID NO:36 (including, but not limited to, the proteins consisting of such sequences, fusion proteins and multivalent proteins) and proteins encoded by allelic variants of SEQ ID NO:1, SEQ ID NO:4, SEQ ID NO:7, SEQ ID NO:10, SEQ ID NO:13, SEQ ID NO:16, SEQ ID NO:19, SEQ ID NO:22, SEQ ID NO:25, SEQ ID NO:28, SEQ ID NO:31 and/or SEQ ID NO:34.
Another embodiment of the present invention is an isolated nucleic acid molecule that hybridizes under stringent hybridization conditions with a C. felis SPI gene. The identifying characteristics of such a gene are heretofore described. A nucleic acid molecule of the present invention can include an isolated natural flea SPI gene or a homolog thereof, the latter of which is described in more detail below. A nucleic acid molecule of the present invention can include one or more regulatory regions, full-length or partial coding regions, or combinations thereof. The minimal size of a nucleic acid molecule of the present invention is the minimal size that can form a stable hybrid with a C. felis SPI gene under stringent hybridization conditions.
In accordance with the present invention, an isolated nucleic acid molecule is a nucleic acid molecule that has been removed from its natural milieu (i.e., that has been subject to human manipulation) and can include DNA, RNA, or derivatives of either DNA or RNA. As such, xe2x80x9cisolatedxe2x80x9d does not reflect the extent to which the nucleic acid molecule has been purified. An isolated flea SPI nucleic acid molecule of the present invention can be isolated from its natural source or can be produced using recombinant DNA technology (e.g., polymerase chain reaction (PCR) amplification, cloning) or chemical synthesis. Isolated SPI nucleic acid molecules can include, for example, natural allelic variants and nucleic acid molecules modified by nucleotide insertions, deletions, substitutions, and/or inversions in a manner such that the modifications do not substantially interfere with the nucleic acid molecule""s ability to encode a SPI protein of the present invention or to form stable hybrids under stringent conditions with natural gene isolates.
A flea SPI nucleic acid molecule homolog can be produced using a number of methods known to those skilled in the art (see, for example, Sambrook et al., ibid.). For example, nucleic acid molecules can be modified using a variety of techniques including, but not limited to, classic mutagenesis and recombinant DNA techniques (e.g., site-directed mutagenesis, chemical treatment, restriction enzyme cleavage, ligation of nucleic acid fragments and/or PCR amplification), synthesis of oligonucleotide mixtures and ligation of mixture groups to xe2x80x9cbuildxe2x80x9d a mixture of nucleic acid molecules and combinations thereof. Nucleic acid molecule homologs can be selected by hybridization with a C. felis SPI gene or by screening for function of a protein encoded by the nucleic acid molecule (e.g., ability to elicit an immune response against at least one epitope of a flea SPI protein or has at least some serine protease inhibitor activity).
An isolated nucleic acid molecule of the present invention can include a nucleic acid sequence that encodes at least one flea SPI protein of the present invention, examples of such proteins being disclosed herein. Although the phrase xe2x80x9cnucleic acid moleculexe2x80x9d primarily refers to the physical nucleic acid molecule and the phrase xe2x80x9cnucleic acid sequencexe2x80x9d primarily refers to the sequence of nucleotides on the nucleic acid molecule, the two phrases can be used interchangeably, especially with respect to a nucleic acid molecule, or a nucleic acid sequence, being capable of encoding a flea SPI protein.
A preferred nucleic acid molecule of the present invention, when administered to an animal, is capable of protecting that animal from infestation by a hematophagous ectoparasite. As will be disclosed in more detail below, such a nucleic acid molecule can be, or can encode, an antisense RNA, a molecule capable of triple helix formation, a ribozyme, or other nucleic acid-based drug compound. In additional embodiments, a nucleic acid molecule of the present invention can encode a protective protein (e.g., a SPI protein of the present invention), the nucleic acid molecule being delivered to the animal, for example, by direct injection (i.e, as a naked nucleic acid) or in a vehicle such as a recombinant virus vaccine or a recombinant cell vaccine.
One embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfSPI11584 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:1 and/or SEQ ID NO:3.
Another embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfsPI21358 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:7 and/or SEQ ID NO:9.
Another embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfSPI31838 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:13 and/or SEQ ID NO:15.
Another embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfSPI41414 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:19 and/or SEQ ID NO:21.
Another embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfSPI51492 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:25 and/or SEQ ID NO:27.
Another embodiment of the present invention is a SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with nucleic acid molecule nfSPI61454 and preferably with a nucleic acid molecule having nucleic acid sequence SEQ ID NO:31 and/or SEQ ID NO:33.
Comparison of nucleic acid sequence SEQ ID NO:4 (i.e., the nucleic acid sequence of the coding strand of nfSPI11191) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:4 showed the most homology, i.e., about 55% identity, with accession number L20792, a putative serine proteinase inhibitor (serpin 1, exon 9 copy 2) gene of Manduca sexta. 
Comparison of nucleic acid sequence SEQ ID NO:10 (i.e., the nucleic acid sequence of the coding strand of nfSPI21197) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:10 showed the most homology, i.e., about 43% identity, with accession number L20790, a putative serine proteinase inhibitor gene (serpin 1, exon 9 copy 1) of Manduca sexta. 
Comparison of nucleic acid sequence SEQ ID NO:16 (i.e., the nucleic acid sequence of the coding strand of nfSPI31260) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:16 showed the most homology, i.e., about 52% identity, with accession number L20792, a putative serine proteinase inhibitor gene (serpin 1, exon 9 copy 2) of Manduca sexta. 
Comparison of nucleic acid sequence SEQ ID NO:22 (i.e., the nucleic acid sequence of the coding strand of nfSPI41179) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:22 showed the most homology, i.e., about 55% identity, with accession number L20793, a putative serine proteinase inhibitor gene (serpin 1, exon 9 unknown copy number) of Manduca sexta. 
Comparison of nucleic acid sequence SEQ ID NO:28 (i.e., the nucleic acid sequence of the coding strand of nfSPI51194) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:28 showed the most homology, i.e., about 45% identity, with accession number L20790, a putative serine proteinase inhibitor gene (serpin 1, exon 9 copy 1) of Manduca sexta. 
Comparison of nucleic acid sequence SEQ ID NO:34 (i.e., the nucleic acid sequence of the coding strand of nfSPI61191) with nucleic acid sequences reported in GenBank indicates that SEQ ID NO:34 showed the most homology, i.e., about 55% identity, with accession number L20792, a putative serine proteinase inhibitor gene (serpin 1, exon 9 copy 2) of Manduca sexta. 
Preferred flea SPI nucleic acid molecules include nucleic acid molecules having a nucleic acid sequence that is at least about 60%, preferably at least about 70%, more preferably at least about 80%, even more preferably at least about 90% and even more preferably at least about 95% identical to nucleic acid sequence SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15,SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:34, and/or SEQ ID 35.
Another preferred nucleic acid molecule of the present invention includes at least a portion of nucleic acid sequence SEQ ID NO: I, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:1, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33. SEQ ID NO:34 and/or SEQ ID 35, that is capable of hybridizing to a C. felis SPI gene of the present invention, as well as allelic variants thereof. A more preferred nucleic acid molecule includes the nucleic acid sequence SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:22, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:28, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33. SEQ ID NO:34 and/or SEQ ID 35, as well as allelic variants thereof. Such nucleic acid molecules can include nucleotides in addition to those included in the SEQ ID NOs, such as, but not limited to, a full-length gene, a full-length coding region, a nucleic acid molecule encoding a fusion protein, or a nucleic acid molecule encoding a multivalent protective compound. Particularly preferred nucleic acid molecules include nfSPI11584, nfSPI11191, nfSPI1376, nfSPI21358, nfSPI21197, nfSPI2376, nfSPI31838, nfSPI31260, nfSPI3391, nfSPI41414, nfSPI41179, nfSPI4376, nfSPI51492, nfSPI51194, nfSPI5376, nfSPI61454, nfSPI61191 and nfSPI6376.
The present invention also includes a nucleic acid molecule encoding a protein having at least a portion of SEQ ID NO:2, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:30, SEQ ID NO:32 and SEQ ID NO:36, including nucleic acid molecules that have been modified to accommodate codon usage properties of the cells in which such nucleic acid molecules are to be expressed.
Knowing the nucleic acid sequences of certain flea SPI nucleic acid molecules of the present invention allows one skilled in the art to, for example, (a) make copies of those nucleic acid molecules, (b) obtain nucleic acid molecules including at least a portion of such nucleic acid molecules (e.g., nucleic acid molecules including full-length genes, full-length coding regions, regulatory control sequences, truncated coding regions), and (c) obtain SPI nucleic acid molecules from other hematophagous ectoparasites. Such nucleic acid molecules can be obtained in a variety of ways including screening appropriate expression libraries with antibodies of the present invention; traditional cloning techniques using oligonucleotide probes of the present invention to screen appropriate libraries or DNA; and PCR amplification of appropriate libraries or DNA using oligonucleotide primers of the present invention. Preferred libraries to screen or from which to amplify nucleic acid molecule include flea hemocyte (i.e., cells found in flea hemolymph), pre-pupal, mixed instar (i.e., a combination of 1st instar larval, 2nd instar larval, 3rd instar larval tissue), or fed or unfed adult cDNA libraries as well as genomic DNA libraries. Similarly, preferred DNA sources to screen or from which to amplify nucleic acid molecules include flea hemocyte, pre-pupal, mixed instar, or fed or unfed adult cDNA and genomic DNA. Techniques to clone and amplify genes are disclosed, for example, in Sambrook et al., ibid.
The present invention also includes nucleic acid molecules that are oligonucleotides capable of hybridizing, under stringent hybridization conditions, with complementary regions of other, preferably longer, nucleic acid molecules of the present invention such as those comprising flea SPI genes or other flea SPI nucleic acid molecules. Oligonucleotides of the present invention can be RNA, DNA, or derivatives of either. The minimum size of such oligonucleotides is the size required for formation of a stable hybrid between an oligonucleotide and a complementary sequence on a nucleic acid molecule of the present invention. Minimal size characteristics are disclosed herein. The present invention includes oligonucleotides that can be used as, for example, probes to identify nucleic acid molecules, primers to produce nucleic acid molecules or therapeutic reagents to inhibit SPI protein production or activity (e.g., as antisense-, triplex formation-, ribozyme- and/or RNA drug-based reagents). The present invention also includes the use of such oligonucleotides to protect animals from disease using one or more of such technologies. Appropriate oligonucleotide-containing therapeutic compositions can be administered to an animal using techniques known to those skilled in the art.
One embodiment of the present invention includes a recombinant vector, which includes at least one isolated nucleic acid molecule of the present invention, inserted into any vector capable of delivering the nucleic acid molecule into a host cell. Such a vector contains heterologous nucleic acid sequences, that is nucleic acid sequences that are not naturally found adjacent to nucleic acid molecules of the present invention and that preferably are derived from a species other than the species from which the nucleic acid molecule(s) are derived. The vector can be either RNA or DNA, either prokaryotic or eukaryotic, and typically is a virus or a plasmid. Recombinant vectors can be used in the cloning, sequencing, and/or otherwise manipulation of flea SPI nucleic acid molecules of the present invention.
One type of recombinant vector, referred to herein as a recombinant molecule, comprises a nucleic acid molecule of the present invention operatively linked to an expression vector. The phrase operatively linked refers to insertion of a nucleic acid molecule into an expression vector in a manner such that the molecule is able to be expressed when transformed into a host cell. As used herein, an expression vector is a DNA or RNA vector that is capable of transforming a host cell and of effecting expression of a specified nucleic acid molecule. Preferably, the expression vector is also capable of replicating within the host cell. Expression vectors can be either prokaryotic or eukaryotic, and are typically viruses or plasmids. Expression vectors of the present invention include any vectors that function (i.e., direct gene expression) in recombinant cells of the present invention, including in bacterial, fungal, endoparasite, insect, other animal, and plant cells. Preferred expression vectors of the present invention can direct gene expression in bacterial, yeast, insect and mammalian cells and more preferably in the cell types disclosed herein.
In particular, expression vectors of the present invention contain regulatory sequences such as transcription control sequences, translation control sequences, origins of replication, and other regulatory sequences that are compatible with the recombinant cell and that control the expression of nucleic acid molecules of the present invention. In particular, recombinant molecules of the present invention include transcription control sequences. Transcription control sequences are sequences which control the initiation, elongation, and termination of transcription. Particularly important transcription control sequences are those which control transcription initiation, such as promoter, enhancer, operator and repressor sequences. Suitable transcription control sequences include any transcription control sequence that can function in at least one of the recombinant cells of the present invention. A variety of such transcription control sequences are known to those skilled in the art. Preferred transcription control sequences include those which function in bacterial, yeast, insect and mammalian cells, such as, but not limited to, tac, lac, trp, trc, oxy-pro, omp/lpp, rrnB, bacteriophage lambda(such as lambda pL and lambda pR and fusions that include such promoters), bacteriophage T7, T7lac, bacteriophage T3, bacteriophage SP6, bacteriophage SP01, metallothionein, alpha-mating factor, Pichia alcohol oxidase, alphavirus subgenomic promoters (such as Sindbis virus subgenomic promoters), antibiotic resistance gene, baculovirus, Heliothis zea insect virus, vaccinia virus, herpesvirus, raccoon poxvirus, other poxvirus, adenovirus, cytomegalovirus (such as intermediate early promoters), simian virus 40, retrovirus, actin, retroviral long terminal repeat, Rous sarcoma virus, heat shock, phosphate and nitrate transcription control sequences as well as other sequences capable of controlling gene expression in prokaryotic or eukaryotic cells. Additional suitable transcription control sequences include tissue-specific promoters and enhancers as well as lymphokine-inducible promoters (e.g., promoters inducible by interferons or interleukins). Transcription control sequences of the present invention can also include naturally occurring transcription control sequences naturally associated with fleas, such as, C. felis. 
Suitable and preferred nucleic acid molecules to include in recombinant vectors of the present invention are as disclosed herein. Preferred nucleic acid molecules to include in recombinant vectors, and particularly in recombinant molecules, include nfSPI11584, nfSPI31260, nfSPI11191, nfSPI1376, nfSPI21358, nfSPI21197, nfSPI2376, nfSPI31838, nfSPI3391, nfSPI41414, nfSPI41179, nfSPI4376, nfSPI51492, nfSPI51194, nfSPI5376, nfSPI61454, nfSPI61191, and nfSPI6376. Particularly preferred recombinant molecules of the present invention include pxcexPR-nfSPI21139, PxcexPR-nfSPI31179, pxcexPR-nfSPI41140, pxcexPR-nfSPI51492 and pxcexPR-nfSPI61136, the production of which are described in the Examples section.
Recombinant molecules of the present invention may also (a) contain secretory signals (i.e., signal segment nucleic acid sequences) to enable an expressed flea protein of the present invention to be secreted from the cell that produces the protein and/or (b) contain fusion sequences which lead to the expression of nucleic acid molecules of the present invention as fusion proteins. Examples of suitable signal segments include any signal segment capable of directing the secretion of a protein of the present invention. Preferred signal segments include, but are not limited to, tissue plasminogen activator (t-PA), interferon, interleukin, growth hormone, histocompatibility and viral envelope glycoprotein signal segments, as well as natural signal segments. Suitable fusion segments encoded by fusion segment nucleic acids are disclosed herein. In addition, a nucleic acid molecule of the present invention can be joined to a fusion segment that directs the encoded protein to the proteosome, such as a ubiquitin fusion segment. Recombinant molecules may also include intervening and/or untranslated sequences surrounding and/or within the nucleic acid sequences of nucleic acid molecules of the present invention.
Another embodiment of the present invention includes a recombinant cell comprising a host cell transformed with one or more recombinant molecules of the present invention. Transformation of a nucleic acid molecule into a cell can be accomplished by any method by which a nucleic acid molecule can be inserted into the cell. Transformation techniques include, but are not limited to, transfection, electroporation, microinjection, lipofection, adsorption, and protoplast fusion. A recombinant cell may remain unicellular or may grow into a tissue, organ or a multicellular organism. Transformed nucleic acid molecules of the present invention can remain extrachromosomal or can integrate into one or more sites within a chromosome of the transformed (i.e., recombinant) cell in such a manner that their ability to be expressed is retained. Preferred nucleic acid molecules with which to transform a cell include flea SPI nucleic acid molecules disclosed herein. Particularly preferred nucleic acid molecules with which to transform a cell include nfSPI11584, nfSPI11191, nfSPI1376, nfSPI21358, nfSPI21197, nfSPI2376, nfSPI31838, nfSPI31260, nfSPI3391, nfSPI41414, nfSPI41179, nfSPI4376, nfSPI51492, nfSPI51194, nfSPI5376, nfSPI61454, nfSPI61191 and nfSPI6376.
Suitable host cells to transform include any cell that can be transformed with a nucleic acid molecule of the present invention. Host cells can be either untransformed cells or cells that are already transformed with at least one nucleic acid molecule (e.g., nucleic acid molecules encoding one or more proteins of the present invention and/or other proteins useful in the production of multivalent vaccines). Host cells of the present invention either can be endogenously (i.e., naturally) capable of producing flea SPI proteins of the present invention or can be capable of producing such proteins after being transformed with at least one nucleic acid molecule of the present invention. Host cells of the present invention can be any cell capable of producing at least one protein of the present invention, and include bacterial, fungal (including yeast), other insect, other animal and plant cells. Preferred host cells include bacterial, mycobacterial, yeast, parasite, insect and mammalian cells. More preferred host cells include Salmonella, Escherichia, Bacillus, Listeria, Saccharomyces, Spodoptera, Mycobacteria, Trichoplusia, BHK (baby hamster kidney) cells, MDCK cells (normal dog kidney cell line for canine herpesvirus cultivation), CRFK cells (normal cat kidney cell line for feline herpesvirus cultivation), CV-1 cells (African monkey kidney cell line used, for example, to culture raccoon poxvirus), COS (e.g., COS-7) cells, and Vero cells. Particularly preferred host cells are Escherichia coli, including E. coli K-12 derivatives; Salmonella typhi; Salmonella typhimurium, including attenuated strains such as UK-1x3987 and SR-11x4072; Spodoptera frugiperda; Trichoplusia ni; BHK cells; MDCK cells; CRFK cells; CV-1 cells; COS cells; Vero cells; and non-tumorigenic mouse myoblast G8 cells (e.g., ATCC CRL 1246). Additional appropriate mammalian cell hosts include other kidney cell lines, other fibroblast cell lines (e.g., human, murine or chicken embryo fibroblast cell lines), myeloma cell lines, Chinese hamster ovary cells, mouse NIH3T3 cells, LMTK31 cells and/or HeLa cells. In one embodiment, the proteins may be expressed as heterologous proteins in myeloma cell lines employing immunoglobulin promoters.
A recombinant cell is preferably produced by transforming a host cell with one or more recombinant molecules, each comprising one or more nucleic acid molecules of the present invention operatively linked to an expression vector containing one or more transcription control sequences. The phrase operatively linked refers to insertion of a nucleic acid molecule into an expression vector in a manner such that the molecule is able to be expressed when transformed into a host cell.
A recombinant molecule of the present invention is a molecule that can include at least one of any nucleic acid molecule heretofore described operatively linked to at least one of any transcription control sequence capable of effectively regulating expression of the nucleic acid molecule(s) in the cell to be transformed, examples of which are disclosed herein. Particularly preferred recombinant molecules include pxcexPR-nfSPI21139, pxcexPR-nSPI31179, pxcexPR-nfSPI41140, pxcexPR-nfSPI51492 and pxcexPR-nfSPI61136.
A recombinant cell of the present invention includes any cell transformed with at least one of any nucleic acid molecule of the present invention. Suitable and preferred nucleic acid molecules as well as suitable and preferred recombinant molecules with which to transform cells are disclosed herein. Particularly preferred recombinant cells include E.coliHB:pxcexPR-nfSPI21139, E.coliHB:pxcexPR-nfSPI31179, E.coliHB:pxcexPR-nfSPI41140, E.coliHB:pxcexPR-nfSPI51492 and E.coliHB:pxcexPR-nfSPI61136. Details regarding the production of these recombinant cells are disclosed herein.
Recombinant cells of the present invention can also be co-transformed with one or more recombinant molecules including flea SPI nucleic acid molecules encoding one or more proteins of the present invention and one or more other nucleic acid molecules encoding other protective compounds, as disclosed herein (e.g., to produce multivalent vaccines).
Recombinant DNA technologies can be used to improve expression of transformed nucleic acid molecules by manipulating, for example, the number of copies of the nucleic acid molecules within a host cell, the efficiency with which those nucleic acid molecules are transcribed, the efficiency with which the resultant transcripts are translated, and the efficiency of post-translational modifications. Recombinant techniques useful for increasing the expression of nucleic acid molecules of the present invention include, but are not limited to, operatively linking nucleic acid molecules to high-copy number plasmids, integration of the nucleic acid molecules into one or more host cell chromosomes, addition of vector stability sequences to plasmids, substitutions or modifications of transcription control signals (e.g., promoters, operators, enhancers), substitutions or modifications of translational control signals (e.g., ribosome binding sites, Shine-Dalgarno sequences), modification of nucleic acid molecules of the present invention to correspond to the codon usage of the host cell, deletion of sequences that destabilize transcripts, and use of control signals that temporally separate recombinant cell growth from recombinant enzyme production during fermentation. The activity of an expressed recombinant protein of the present invention may be improved by fragmenting, modifying, or derivatizing nucleic acid molecules encoding such a protein.
Isolated SPI proteins of the present invention can be produced in a variety of ways, including production and recovery of natural proteins, production and recovery of recombinant proteins, and chemical synthesis of the proteins. In one embodiment, an isolated protein of the present invention is produced by culturing a cell capable of expressing the protein under conditions effective to produce the protein, and recovering the protein. A preferred cell to culture is a recombinant cell of the present invention. Effective culture conditions include, but are not limited to, effective media, bioreactor, temperature, pH and oxygen conditions that permit protein production. An effective medium refers to any medium in which a cell is cultured to produce a flea SPI protein of the present invention. Such medium typically comprises an aqueous medium having assimilable carbon, nitrogen and phosphate sources, and appropriate salts, minerals, metals and other nutrients, such as vitamins. Cells of the present invention can be cultured in conventional fermentation bioreactors, shake flasks, test tubes, microtiter dishes, and petri plates. Culturing can be carried out at a temperature, pH and oxygen content appropriate for a recombinant cell. Such culturing conditions are within the expertise of one of ordinary skill in the art. Examples of suitable conditions are included in the Examples section.
Depending on the vector and host system used for production, resultant proteins of the present invention may either remain within the recombinant cell; be secreted into the fermentation medium; be secreted into a space between two cellular membranes, such as the periplasmic space in E. coli; or be retained on the outer surface of a cell or viral membrane. The phrase xe2x80x9crecovering the proteinxe2x80x9d, as well as similar phrases, refers to collecting the whole fermentation medium containing the protein and need not imply additional steps of separation or purification. Proteins of the present invention can be purified using a variety of standard protein purification techniques, such as, but not limited to, affinity chromatography, ion exchange chromatography, filtration, electrophoresis, hydrophobic interaction chromatography, gel filtration chromatography, reverse phase chromatography, concanavalin A chromatography, chromatofocusing and differential solubilization. Proteins of the present invention are preferably retrieved in xe2x80x9csubstantially purexe2x80x9d form. As used herein, xe2x80x9csubstantially purexe2x80x9d refers to a purity that allows for the effective use of the protein as a therapeutic composition or diagnostic. A therapeutic composition for animals, for example, should exhibit no substantial toxicity and preferably should be capable of stimulating the production of antibodies in a treated animal.
The present invention also includes isolated (i.e., removed from their natural milieu) antibodies that selectively bind to a flea SPI protein of the present invention or a mimetope thereof (i.e., anti-flea SPI antibodies). As used herein, the term xe2x80x9cselectively binds toxe2x80x9d a SPI protein refers to the ability of antibodies of the present invention to preferentially bind to specified proteins and mimetopes thereof of the present invention. Binding can be measured using a variety of methods standard in the art including enzyme immunoassays (e.g., ELISA), immunoblot assays, etc.; see, for example, Sambrook et al., ibid. An anti-flea SPI antibody preferably selectively binds to a flea SPI protein in such a way as to reduce the activity of that protein.
Isolated antibodies of the present invention can include antibodies in a bodily fluid (such as, but not limited to, serum), or antibodies that have been purified to varying degrees. Antibodies of the present invention can be polyclonal or monoclonal. Functional equivalents of such antibodies, such as antibody fragments and genetically-engineered antibodies (including single chain antibodies or chimeric antibodies that can bind to more than one epitope) are also included in the present invention.
A preferred method to produce antibodies of the present invention includes (a) administering to an animal an effective amount of a protein, peptide or mimetope thereof of the present invention to produce the antibodies and (b) recovering the antibodies. In another method, antibodies of the present invention are produced recombinantly using techniques as heretofore disclosed to produce flea SPI proteins of the present invention. Antibodies raised against defined proteins or mimetopes can be advantageous because such antibodies are not substantially contaminated with antibodies against other substances that might otherwise cause interference in a diagnostic assay or side effects if used in a therapeutic composition.
Antibodies of the present invention have a variety of potential uses that are within the scope of the present invention. For example, such antibodies can be used (a) as therapeutic compounds to passively immunize an animal in order to protect the animal from hematophagous ectoparasites susceptible to treatment by such antibodies and/or (b) as tools to screen expression libraries and/or to recover desired proteins of the present invention from a mixture of proteins and other contaminants. Furthermore, antibodies of the present invention can be used to target cytotoxic agents to hematophagous ectoparasite such as those disclosed herein in order to directly kill such hematophagous ectoparasites. Targeting can be accomplished by conjugating (i.e., stably joining) such antibodies to the cytotoxic agents using techniques known to those skilled in the art. Suitable cytotoxic agents are known to those skilled in the art.
One embodiment of the present invention is a therapeutic composition that, when administered to an animal in an effective manner, is capable of protecting that animal from infestation by hematophagous ectoparasites. Therapeutic compositions of the present invention include at least one of the following protective compounds: an isolated flea SPI protein (including a peptide of a flea SPI protein capable of inhibiting serine protease activity), a mimetope of a flea SPI protein, an isolated SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with a Ctenocephalides felis SPI gene, an isolated antibody that selectively binds to a flea SPI protein, and inhibitors of flea SPI activity (including flea SPI protein substrate analogs, such as serine proteases or serine protease analogs). Preferred hematophagous ectoparasites to target are heretofore disclosed. Examples of protective compounds (e.g., proteins, mimetopes, nucleic acid molecules, antibodies, and inhibitors) are disclosed herein.
Suitable inhibitors of SPI activity are compounds that interact directly with a SPI protein active site, thereby inhibiting that SPI""s activity, usually by binding to or otherwise interacting with or otherwise modifying the SPI""s active site. SPI inhibitors can also interact with other regions of the SPI protein to inhibit SPI activity, for example, by allosteric interaction. Inhibitors of SPIs are usually relatively small compounds and as such differ from anti-SPI antibodies. Preferably, a SPI inhibitor of the present invention is identified by its ability to bind to, or otherwise interact with, a flea SPI protein, thereby inhibiting the activity of the flea SPI.
Inhibitors of a SPI can be used directly as compounds in compositions of the present invention to treat animals as long as such compounds are not harmful to host animals being treated. Inhibitors of a SPI protein can also be used to identify preferred types of flea SPI proteins to target using compositions of the present invention, for example by affinity chromatography. Preferred inhibitors of a SPI of the present invention include, but are not limited to, flea SPI substrate analogs, and other molecules that bind to a flea SPI (e.g., to an allosteric site) in such a manner that SPI activity of the flea SPI is inhibited. A SPI substrate analog refers to a compound that interacts with (e.g., binds to, associates with, modifies) the active site of a SPI protein. A preferred SPI substrate analog inhibits SPI activity. SPI substrate analogs can be of any inorganic or organic composition, and, as such, can be, but are not limited to, peptides, nucleic acids, and peptidomimetic compounds. SPI substrate analogs can be, but need not be, structurally similar to a SPI protein""s natural substrate as long as they can interact with the active site of that SPI protein. SPI substrate analogs can be designed using computer-generated structures of SPI proteins of the present invention or computer structures of SPI proteins"" natural substrates. Substrate analogs can also be obtained by generating random samples of molecules, such as oligonucleotides, peptides, peptidomimetic compounds, or other inorganic or organic molecules, and screening such samples by affinity chromatography techniques using the corresponding binding partner, (e.g., a flea SPI or anti-flea serine protease antibody). A preferred SPI substrate analog is a peptidomimetic compound (i.e., a compound that is structurally and/or functionally similar to a natural substrate of a SPI of the present invention, particularly to the region of the substrate that interacts with the SPI active site, but that inhibits SPI activity upon interacting with the SPI active site).
SPI peptides, mimetopes and substrate analogs, as well as other protective compounds, can be used directly as compounds in compositions of the present invention to treat animals as long as such compounds are not harmful to the animals being treated.
The present invention also includes a therapeutic composition comprising at least one flea SPI-based compound of the present invention in combination with at least one additional compound protective against hematophagous ectoparasite infestation. Examples of such compounds are disclosed herein.
In one embodiment, a therapeutic composition of the present invention can be used to protect an animal from hematophagous ectoparasite infestation by administering such composition to a hematophagous ectoparasite, such as to a flea, in order to prevent infestation. Such administration could be orally or by developing transgenic vectors capable of producing at least one therapeutic composition of the present invention. In another embodiment, a hematophagous ectoparasite, such as a flea, can ingest therapeutic compositions, or products thereof, present in the blood of a host animal that has been administered a therapeutic composition of the present invention.
Compositions of the present invention can be administered to any animal susceptible to hematophagous ectoparasite infestation (i.e., a host animal), including warm-blooded animals. Preferred animals to treat include mammals and birds, with cats, dogs, humans, cattle, chinchillas, ferrets, goats, mice, minks, rabbits, raccoons, rats, sheep, squirrels, swine, chickens, ostriches, quail and turkeys as well as other furry animals, pets and/or economic food animals, being more preferred. Particularly preferred animals to protect are cats and dogs.
In accordance with the present invention, a host animal (i.e., an animal that is or is capable of being infested with a hematophagous ectoparasite) is treated by administering to the animal a therapeutic composition of the present invention in such a manner that the composition itself (e.g., an inhibitor of a SPI protein, a SPI synthesis suppressor (i.e., a compound that decreases the production of SPI in the hematophagous ectoparasite), an SPI mimetope, or an anti-hematophagous ectoparasite SPI antibody) or a product generated by the animal in response to administration of the composition (e.g., antibodies produced in response to a flea SPI protein or nucleic acid molecule vaccine, or conversion of an inactive inhibitor xe2x80x9cprodrugxe2x80x9d to an active inhibitor of a SPI protein) ultimately enters the hematophagous ectoparasite. A host animal is preferably treated in such a way that the compound or product thereof enters the blood stream of the animal. Hematophagous ectoparasites are then exposed to the composition or product when they feed from the animal. For example, flea SPI protein inhibitors administered to an animal are administered in such a way that the inhibitors enter the blood stream of the animal, where they can be taken up by feeding fleas. In another embodiment, when a host animal is administered a flea SPI protein or nucleic acid molecule vaccine, the treated animal mounts an immune response resulting in the production of antibodies against the SPI protein (i.e., anti-flea SPI antibodies) which circulate in the animal""s blood stream and are taken up by hematophagous ectoparasites upon feeding. Blood taken up by hematophagous ectoparasites enters the hematophagous ectoparasites where compounds of the present invention, or products thereof, such as anti-flea SPI antibodies, flea SPI protein inhibitors, flea mimetopes and/or SPI synthesis suppressors, interact with, and reduce SPI protein activity in the hematophagous ectoparasite.
The present invention also includes the ability to reduce larval hematophagous ectoparasite infestation in that when hematophagous ectoparasites feed from a host animal that has been administered a therapeutic composition of the present invention, at least a portion of compounds of the present invention, or products thereof, in the blood taken up by the hematophagous ectoparasite are excreted by the hematophagous ectoparasite in feces, which is subsequently ingested by hematophagous ectoparasite larvae. In particular, it is of note that flea larvae obtain most, if not all, of their nutrition from flea feces.
In accordance with the present invention, reducing SPI protein activity in a hematophagous ectoparasite can lead to a number of outcomes that reduce hematophagous ectoparasite burden on treated animals and their surrounding environments. Such outcomes include, but are not limited to, (a) reducing the viability of hematophagous ectoparasites that feed from the treated animal, (b) reducing the fecundity of female hematophagous ectoparasites that feed from the treated animal, (c) reducing the reproductive capacity of male hematophagous ectoparasites that feed from the treated animal, (d) reducing the viability of eggs laid by female hematophagous ectoparasites that feed from the treated animal, (e) altering the blood feeding behavior of hematophagous ectoparasites that feed from the treated animal (e.g., hematophagous ectoparasites take up less volume per feeding or feed less frequently), (f) reducing the viability of hematophagous ectoparasite larvae (e.g., by decreasing feeding behavior, inhibiting growth, inhibiting (e.g., slowing or blocking) molting, and/or otherwise inhibiting maturation to adults).
Therapeutic compositions of the present invention can be formulated in an excipient that the animal to be treated can tolerate. Examples of such excipients include water, saline, Ringer""s solution, dextrose solution, Hank""s solution, and other aqueous physiologically balanced salt solutions. Nonaqueous vehicles, such as fixed oils, sesame oil, ethyl oleate, or triglycerides may also be used. Other useful formulations include suspensions containing viscosity enhancing agents, such as sodium carboxymethylcellulose, sorbitol, or dextran. Excipients can also contain minor amounts of additives, such as substances that enhance isotonicity and chemical stability. Examples of buffers include phosphate buffer, bicarbonate buffer and Tris buffer, while examples of preservatives include thimerosal,xe2x80x94or o-cresol, formalin and benzyl alcohol. Standard formulations can either be liquid injectables or solids which can be taken up in a suitable liquid as a suspension or solution for injection. Thus, in a non-liquid formulation, the excipient can comprise dextrose, human serum albumin, preservatives, etc., to which sterile water or saline can be added prior to administration.
In one embodiment of the present invention, a therapeutic composition can include an adjuvant. Adjuvants are agents that are capable of enhancing the immune response of an animal to a specific antigen. Suitable adjuvants include, but are not limited to, cytokines, chemokines, and compounds that induce the production of cytokines and chemokines (e.g., granulocyte macrophage colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CSF), macrophage colony stimulating factor (M-CSF), colony stimulating factor (CSF), erythropoietin (EPO), interleukin 2 (IL-2), interleukin-3 (IL-3), interleukin 4 (IL-4), interleukin 5 (IL-5), interleukin 6 (IL-6interleukin 7 (IL-7), interleukin 8 (IL-8), interleukin 10 (IL-10), interleukin 12 (IL-12), interferon gamma, interferon gamma inducing factor I (IGIF), transforming growth factor beta, RANTES (regulated upon activation, normal T cell expressed and presumably secreted), macrophage inflammatory proteins (e.g., MIP-1 alpha and MIP-1 beta), and Leishmania elongation initiating factor (LEIF); bacterial components (e.g., endotoxins, in particular superantigens, exotoxins and cell wall components); aluminum-based salts; calcium-based salts; silica; polynucleotides; toxoids; serum proteins, viral coat proteins; block copolymer adjuvants (e.g., Hunter""s Titertmax(trademark) adjuvant (Vaxcel(trademark), Inc. Norcross, Ga.), Ribi adjuvants (Ribi ImmunoChem Research, Inc., Hamilton, Mont.); and saponins and their derivatives (e.g., Quil A (Superfos Biosector A/S, Denmark). Protein adjuvants of the present invention can be delivered in the form of the protein themselves or of nucleic acid molecules encoding such proteins using the methods described herein.
In one embodiment of the present invention, a therapeutic composition can include a carrier. Carriers include compounds that increase the half-life of a therapeutic composition in the treated animal. Suitable carriers include, but are not limited to, polymeric controlled release vehicles, biodegradable implants, liposomes, bacteria, viruses, other cells, oils, esters, and glycols.
One embodiment of the present invention is a controlled release formulation that is capable of slowly releasing a composition of the present invention into an animal. As used herein, a controlled release formulation comprises a composition of the present invention in a controlled release vehicle. Suitable controlled release vehicles include, but are not limited to, biocompatible polymers, other polymeric matrices, capsules, microcapsules, microparticles, bolus preparations, osmotic pumps, diffusion devices, liposomes, lipospheres, and transdermal delivery systems. Other controlled release formulations of the present invention include liquids that, upon administration to an animal, form a solid or a gel in situ. Preferred controlled release formulations are biodegradable (i.e., bioerodible).
A preferred controlled release formulation of the present invention is capable of releasing a composition of the present invention into the blood of an animal at a constant rate sufficient to attain therapeutic dose levels of the composition to protect an animal from hematophagous ectoparasite infestation. The therapeutic composition is preferably released over a period of time ranging from about 1 to about 12 months. A preferred controlled release formulation of the present invention is capable of effecting a treatment preferably for at least about 1 month, more preferably for at least about 3 months, even more preferably for at least about 6 months, even more preferably for at least about 9 months, and even more preferably for at least about 12 months.
Acceptable protocols to administer therapeutic compositions of the present invention in an effective manner include individual dose size, number of doses, frequency of dose administration, and mode of administration. Determination of such protocols can be accomplished by those skilled in the art. A suitable single dose is a dose that is capable of protecting an animal from disease when administered one or more times over a suitable time period. For example, a preferred single dose of a protein, mimetope or antibody therapeutic composition is from about 1 microgram (xcexcg) to about 10 milligrams (mg) of the therapeutic composition per kilogram body weight of the animal. Booster vaccinations can be administered from about 2 weeks to several years after the original administration. Booster administrations preferably are administered when the immune response of the animal becomes insufficient to protect the animal from disease. A preferred administration schedule is one in which from about 10 xcexcg to about 1 mg of the therapeutic composition per kg body weight of the animal is administered from about one to about two times over a time period of from about 2 weeks to about 12 months. Modes of administration can include, but are not limited to, subcutaneous, intradermal, intravenous, intranasal, oral, transdermal, intraocular and intramuscular routes.
According to one embodiment, a nucleic acid molecule of the present invention can be administered to an animal in a fashion to enable expression of that nucleic acid molecule into a protective protein or protective RNA (e.g., antisense RNA, ribozyme, triple helix forms or RNA drug) in the animal. Nucleic acid molecules can be delivered to an animal in a variety of methods including, but not limited to, (a) administerin a naked (i.e., not packaged in a viral coat or cellular membrane) nucleic acid vaccine (e.g., as naked DNA or RNA molecules, such as is taught, for example in Wolff et al., 1990, Science 247, 1465-1468) or (b) administering a nucleic acid molecule packaged as a recombinant virus vaccine or as a recombinant cell vaccine (i.e., the nucleic acid molecule is delivered by a viral or cellular vehicle).
A naked nucleic acid vaccine of the present invention includes a nucleic acid molecule of the present invention and preferably includes a recombinant molecule of the present invention that preferably is replication, or otherwise amplification, competent. A naked nucleic acid vaccine of the present invention can comprise one or more nucleic acid molecules of the present invention in the form of, for example, a bicistronic recombinant molecule having, for example one or more internal ribosome entry sites. Preferred naked nucleic acid vaccines include at least a portion of a viral genome (i.e., a viral vector). Preferred viral vectors include those based on alphaviruses, poxviruses, adenoviruses, herpesviruses, and retroviruses, with those based on alphaviruses (such as Sindbis or Semliki virus), species-specific herpesviruses and species-specific poxviruses being particularly preferred. Any suitable transcription control sequence can be used, including those disclosed as suitable for protein production. Particularly preferred transcription control sequence include cytomegalovirus intermediate early (preferably in conjunction with Intron-A), Rous Sarcoma Virus long terminal repeat, and tissue-specific transcription control sequences, as well as transcription control sequences endogenous to viral vectors if viral vectors are used. The incorporation of xe2x80x9cstrongxe2x80x9d poly(A) sequences are also preferred.
Naked nucleic acid vaccines of the present invention can be administered in a variety of ways, with intramuscular, subcutaneous, intradermal, transdermal, intranasal and oral routes of administration being preferred. A preferred single dose of a naked nucleic acid vaccines ranges from about 1 nanogram (ng) to about 100 xcexcg, depending on the route of administration and/or method of delivery, as can be determined by those skilled in the art. Suitable delivery methods include, for example, by injection, as drops, aerosolized and/or topically. Naked DNA of the present invention can be contained in an aqueous excipient (e.g., phosphate buffered saline) alone or a carrier (e.g., lipid-based vehicles).
A recombinant virus vaccine of the present invention includes a recombinant molecule of the present invention that is packaged in a viral coat and that can be expressed in an animal after administration. Preferably, the recombinant molecule is packaging-deficient and/or encodes an attenuated virus. A number of recombinant viruses can be used, including, but not limited to, those based on alphaviruses, poxviruses, adenoviruses, herpesviruses, and retroviruses. Preferred recombinant virus vaccines are those based on alphaviruses (such as Sindbis virus), raccoon poxviruses, species-specific herpesviruses and species-specific poxviruses. An example of methods to produce and use alphavirus recombinant virus vaccines is disclosed in PCT Publication No. WO 94/17813, by Xiong et al., published Aug. 18, 1994, which is incorporated by reference herein in its entirety.
When administered to an animal, a recombinant virus vaccine of the present invention infects cells within the immunized animal and directs the production of a protective protein or RNA nucleic acid molecule that is capable of protecting the animal from hematophagous ectoparasite infestation. For example, a recombinant virus vaccine comprising a flea SPI nucleic acid molecule of the present invention is administered according to a protocol that results in the animal producing a sufficient immune response to protect itself from hematophagous ectoparasite infestation. A preferred single dose of a recombinant virus vaccine of the present invention is from about 1xc3x97104 to about 1xc3x97107 virus plaque forming units (pfu) per kilogram body weight of the animal. Administration protocols are similar to those described herein for protein-based vaccines, with subcutaneous, intramuscular, intranasal and oral administration routes being preferred.
A recombinant cell vaccine of the present invention includes recombinant cells of the present invention that express at least one protein of the present invention. Preferred recombinant cells for this embodiment include Salmonella, E. coli, Listeria, Mycobacterium, S. frugiperda, yeast, (including Saccharomyces cerevisiae), BHK, CV-1, myoblast G8, COS (e.g., COS-7), Vero, MDCK and CRFK recombinant cells. Recombinant cell vaccines of the present invention can be administered in a variety of ways but have the advantage that they can be administered orally, preferably at doses ranging from about 108 to about 1012 cells per kilogram body weight. Administration protocols are similar to those described herein for protein-based vaccines. Recombinant cell vaccines can comprise whole cells, cells stripped of cell walls or cell lysates.
The efficacy of a therapeutic. composition of the present invention to protect an animal from hematophagous ectoparasite infestation can be tested in a variety of ways including, but not limited to, detection of anti-flea SPI antibodies (using, for example, proteins or mimetopes of the present invention), detection of cellular immunity within the treated animal, or challenge of the treated animal with hematophagous ectoparasites to determine whether, for example, the feeding, fecundity or viability of the hematophagous ectoparasites feeding from the treated animal is disrupted. Challenge studies can include attachment of chambers containing fleas onto the skin of the treated animal. In one embodiment, therapeutic compositions can be tested in animal models such as mice. Such techniques are known to those skilled in the art.
One preferred embodiment of the present invention is the use of flea SPI proteins, mimetopes, nucleic acid molecules, antibodies and inhibitory compounds of the present invention, to protect an animal from hematophagous ectoparasite infestation. Preferred protective compounds of the present invention include, but are not limited to, an isolated flea SPI protein or a mimetope thereof, an isolated SPI nucleic acid molecule that hybridizes under stringent hybridization conditions with a Ctenocephalides felis SPI gene, an isolated antibody that selectively binds to a flea SPI and/or an inhibitor of flea SPI activity (such as, but not limited to, an SPI substrate analog). Additional protection may be obtained by administering additional protective compounds, including other proteins, nucleic acid molecules, antibodies and inhibitory compounds, as disclosed herein.
An inhibitor of SPI activity can be identified using flea SPI proteins of the present invention. One embodiment of the present invention is a method to identify a compound capable of inhibiting SPI activity of a flea. Such a method includes the steps of (a) contacting (e.g., combining, mixing) an isolated flea SPI protein, preferably a C. felis SPI protein, with a putative inhibitory compound under conditions in which, in the absence of the compound, the protein has SPI activity, and (b) determining if the putative inhibitory compound inhibits the SPI activity. Putative inhibitory compounds to screen include small organic molecules, antibodies (including mimetopes thereof) and substrate analogs. Methods to determine SPI activity are known to those skilled in the art.
The present invention also includes a test kit to identify a compound capable of inhibiting SPI activity of a flea. Such a test kit includes an isolated flea SPI protein, preferably a C. felis SPI protein, having SPI activity and a means for determining the extent of inhibition of SPI activity in the presence of (i.e., effected by) a putative inhibitory compound. Such compounds are also screened to identify those that are substantially not toxic in host animals.
SPI inhibitors isolated by such a method, and/or test kit, can be used to inhibit any SPI protein that is susceptible to such an inhibitor. Preferred SPI enzymes proteins to inhibit are those produced by fleas. A particularly preferred inhibitor of a SPI protein of the present invention is capable of protecting an animal from flea infestation. Effective amounts and dosing regimens can be determined using techniques known to those skilled in the art.
The following examples are provided for the purposes of illustration and are not intended to limit the scope of the present invention.